Conventional inkjet printing apparatuses (e.g., inkjet printers) typically include one or more printheads in which ink is stored. Such printheads have one or more ink reservoirs in fluid communication with nozzles through which ink exits the printhead toward a print medium. In many cases, the nozzles are located in one or more nozzle plates coupled to a body of the printhead.
A problem common to many inkjet printheads is the ability of air within the printhead to block the passage of ink. When an empty or partially empty printhead is filled with ink, air can be expelled from the printhead (e.g., through the printhead nozzles described above) to prevent such blockage. However, in many cases, some air can become trapped in one or more locations in the printhead. For example, air bubbles can become trapped within the ink reservoirs and/or between one or more filters and the downstream nozzles.
To promote evacuation of air from the printhead, many printheads are filled with ink when such printheads are at least partially inverted. In such orientations, ink can be introduced into the printhead, forcing air from the printhead through the nozzles. However, air bubbles can still remain trapped in corners, recesses, and other positions within the inverted printhead, and can move to block ink flow when the printhead is later installed in an operating orientation. For example, ink can be introduced into an inverted ink reservoir having a filter tower covered by a filter. However, air bubbles can remain in the filter tower after the ink reservoir has been filled with ink, and can later migrate to cover at least a portion of the filter when the printhead is later installed in an operating orientation. In such cases, the printhead can lose prime, thereby stopping ink flow and causing printhead failure.